2-deoxy-scyllo-inosose (hereinafter also referred to as DOI) is a useful substance used as a pharmaceutical raw material and a chemical industry resource. For example, according to Japanese Patent Application Laid-Open (JP-A) No. 2000-236881, it is shown that 2-deoxy-scyllo-inosose can be produced from glucose-6-phosphate (G-6-P) through a short process using a recombinant DOI synthase obtained using Escherichia coli. Furthermore, for example, according to International Publication (WO) No. 2006/109479, a method of producing DOI from glucose in a single step by using Escherichia coli expressing a DOI synthase has been developed. This has enabled the production of DOI from glucose obtained from a plant-derived resource.
However, according to the Journal of Biotechnology, Vol. 129, pp. 502-509 (2007), it has been found that the DOI production method described in WO No. 2006/109479 not only uses glucose as the raw material but also separately requires mannitol, which is a rare and expensive sugar, for the proliferation and growth of the bacterial cell. In the above Journal, it has been shown that simple expression of the DOI synthase in a wild type Escherichia coli produces only 1.5 g/L of DOI, and to achieve high productivity (29.5 g/L), it is necessary to simultaneously disrupt three enzyme genes present in Escherichia coli; namely, phosphoglucose isomerase (pgi), glucose-6-phosphate-1-dehydrogenase (zwf), and phosphoglucomutase (pgm). Thus, it has been concluded that since all the metabolic pathways through which glucose enters the glycolytic pathway are blocked, a sugar (such as mannitol) that is separately usable in the glycolytic pathway is required for the proliferation and growth of the bacterial cell. In addition, to obtain similar high productivity of DOI, it may be enough to merely simultaneously disrupt the two genes pgi and zwf. However, even in this case, it is clear that when glucose is the only carbon source, the bacterial cell cannot proliferate, so that mannitol remains necessary for the proliferation and growth thereof.
Meanwhile, sucrose is known as a sugar raw material that is less expensive than glucose. Sucrose is a main component of blackstrap molasses. It is expected that Escherichia coli producing DOI by assimilating sucrose will be useful in the production of inexpensive DOI that is useful for industrial purposes, although to date no bacteria have existed that produce DOI by sucrose assimilation.
For example, in JP-A No. 2001-346578, the mechanism of sucrose assimilation in a microorganism is roughly classified into two systems: the sucrose PTS (Phosphoenolpyruvate: Carbohydrate Phosphotransferase System) and the sucrose non-PTS. In the case of assimilation through the sucrose non-PTS, the microorganism incorporates sucrose as it is and decomposes it into glucose and fructose. On the other hand, in assimilation through the sucrose PTS, the microorganism incorporates sucrose by means of phosphorylation of sucrose to convert it to sucrose-6-phosphate, and then decomposes it into glucose-6-phosphate and fructose within itself.
In other words, through either mechanism, sucrose-derived fructose appears in the microorganism, first in its non-phosphorylated form. Then, to allow fructose that is not phosphorylated (hereinafter referred to as non-phosphorylated fructose) to be taken into the glycolytic pathway, fructose needs to be isomerized into glucose or phosphorylated. However, FEMS Yeast Research, Vol. 5, pp. 1055-1062 (2005), Proceedings of the National Academy of Sciences of the United States of America (PNAS), Vol. 98(26), pp. 15257-15259 (2001), and the Journal of Bacteriology, Vol. 184(19), pp. 5307-5316 (2002) have suggested that when the microorganism is Escherichia coli, the activity of isomerizing non-phosphorylated fructose into glucose and the activity of phosphorylating fructose are both extremely low. Therefore, even if non-phosphorylated fructose successfully appears in Escherichia coli, it has not been expected that Escherichia coli will assimilate the non-phosphorylated fructose unless other means is provided.
The Canadian Journal of Microbiology, Vol. 45, pp. 418-422 (1999) has disclosed that introducing only a sucrose hydrolase gene (cscA) into Escherichia coli has enabled the proliferation of Escherichia coli with sucrose as a raw material. On the other hand, one important thing in DOI production by Escherichia coli using sucrose as a raw material is that the bacterial cell proliferation and growth is achieved by using sucrose-derived fructose. However, the above literature has disclosed consistently only information regarding the introduction of sucrose and glucose into the bacterial cell, and has not disclosed any data on the extent of assimilation of sucrose-derived fructose.